Rotational grazing is generally considered ecologically beneficial because of its potential to build soil and maintain diverse and robust plant communities. Grass-based farming (i.e. pastures for grazing and haying), however, can come in conflict with the ecology of other organisms such as grassland birds.

Some have suggested that refuges – areas that aren’t grazed by cattle during the nesting season – may help reconcile the use of these ecosystems by cattle and grassland birds including the threatened bobolink.

A Bobolink nest built on the ground in a cattle pasture. Photo: Gerald Morris, BECO

To assess whether strategically placed bobolink refuges can have meaningful impact on conservation efforts for this species, Bird Ecology and Conservation Ontario (BECO), a non-profit organization dedicated to the conservation of birds in Ontario through the use of ecological research, is teaming up with the Ontario Soil and Crop Improvement Association (OSCIA) on a 2-year study in the Ottawa Valley. The project is funded by the Government of Canada through the Species at Risk Partnerships on Agricultural Lands initiative.

Starting in May 2016, wildlife biologists with BECO worked with 5 farmers on 8 pastures that are each rotationally grazed by 1 herd of beef cattle (herd sizes vary, as do stocking density, rest period, etc.). Across the 2-year study, each pasture has 1 year of treatment, when ~2 hectares remains un-grazed during the bobolink breeding season (mid-May to mid-July) to provide refuge habitat, and 1 year of control, when all paddocks are grazed during the nesting period. When possible, the order of refuge treatment vs. control was randomly assigned.

In May, June and July, the BECO crew located and monitored breeding success in nearly 90 bobolink territories. In these territories, they found and monitored 32 nests, of which 15 fledged young while the others were predated or destroyed by cattle trampling. After year 2, they will compare the proportion of bobolink that fledged young in each pasture under treatment and control.

The conservation implications of this study are important and complex. If refuges are effective at supporting bobolink conservation in pastures, what does this mean for grass-based farmers who may already feel the burden of conservation efforts in an agricultural landscape composed primarily of monocultures and field crops? If refuges don’t improve bobolink reproductive success, then what does the future hold for this charismatic grassland species?